Lutgarda Yi Sun-i, also called ‘Yu-hui` was born in 1782 to a well-known noble family. She lived a life of ardent faith from the time she was a young girl. Charles Yi Gyeong-do who was martyred in 1801 and Paul Yi Gyeong-eon who was martyred in 1827 were her brothers. John Yu Jung-cheol who was martyred in 1801 was her husband.

Matthew Yi Yun-ha, Lutgarda Yi`s father, inherited the scholarship of his maternal grandfather Yi Ik who was a renowned scholar of that time. Matthew Yi became a Catholic in 1784, soon after Catholicism was introduced to Korea, when he met with Ambrose Kwon Chol-sin, his brother-in-law, Francis Xavier Kwon Il-sin and Peter Yi Seung-hun. It was in this family atmosphere that Lutgarda Yi`s mother studied the catechism and became a Catholic. She then taught the catechism as well as basic education to her young daughter Lutgarda from an early age.

When her father died in 1793, Lutgarda lived with her mother and devoted herself to practicing the Church`s teaching and saving souls. In 1795, she received her First Holy Communion from Father James Zhou Wen-mo. She spent four days in preparation, praying and studying the catechism.

Afterwards, Lutgarda Yi concentrated her life on prayer, adoration of the Blessed Sacrament and striving after virtue. She then made a vow of chastity to her heavenly spouse, Jesus Christ. However, in the society of that time it was extremely difficult for a young woman to remain single.

In 1797, when she was 15 years old, Lutgarda confessed to her mother that she had decided to keep her vow of chastity for God. Though surprised, her mother agreed with her decision and consulted Father James Zhou about it. Father James Zhou remembered that John Yu Jung-cheol also wanted to live a life of celibacy. So he immediately sent a messenger and arranged their marriage.

In September 1798, Lutgarda Yi went to her husband`s native place, Chonam in Jeonju (now, Namgye-ri, Iseo-myeon, Wanju-gun, Jeonbuk) and made a vow in the presence of her parents-in-law with John Yu, her husband, to live a celibate life. Whenever her husband was tempted to break his vow of chastity she helped him to overcome it by prayer and meditation. They pledged to die as martyrs together.

Soon after, in 1801, the Shinyu Persecution broke out and the police invaded Chonam. First they arrested Augustine Yu Hang-geom, her father-in-law and took him to Seoul. Then they arrested her husband John Yu and took him to Jeonju.

Lutgarda Yi herself was arrested about the middle of September together with the rest of her family. They were all taken to Jeonju. She encouraged her family saying, "We will all go to heaven together." This is well reflected in her letter to her elder sisters which she wrote in prison:

"We five people were unanimous in our firm resolution to give our lives completely to God even to the point of martyrdom. By opening our hearts to one another we came to know that we all have the same burning desire to die for God …… and so, all our regrets and anxieties vanished. Each day, we are nourished by divine grace and love, and divine joy grows in our hearts. It seems that there are no worries left in our hearts."

The chief official of Jeonju requested the royal court`s decision on Lutgarda Yi and her relatives. In response, the royal court sent a government official to Jeonju immediately, to take charge of this case. Consequently, Lutgarda Yi was condemned to exile and left for Hamgyeong-do. On behalf of her family, Lutgarda Yi requested the authorities to punish them according to the national law. However, her request was not granted.

Not long after they left for the land of exile, the police followed them and arrested them again. Lutgarda Yi could not hide her joy and said; "Finally, I can die a martyr."

She was taken to the governor again and was sentenced to death. She was imprisoned after being beaten cruelly. However, she did not feel any pain and her wounds were completely healed in four or five days.

The governor finally requested the royal court to pronounce the execution and very soon the royal sanction came. On January 31, 1802 (December 28, 1801 by the Lunar calendar). Lutgarda Yi was taken to the execution ground in Jeonju, called `Supjeongi`, with her relatives. She was beheaded and died a martyr. Lutgarda Yi was 20 years old.